可以通过34461A将PSU连接到PCB并限制电流吗

这是一个难以回答的问题，还是我在错误的论坛上发布了这个问题？



     以下为原文

  Is it a difficult question to reply or did I post the question on a wrong forum?

坦率地说，你的问题有点奇怪。
我会尽力回答，希望没有误解你的问题。
我担心你对当前输入的工作方式有错误的概念。
任何DMM的电流范围仅具有内部分流器（电阻器）。
它既不是电流吸收器/源，也不是这种分流器能够以受控方式限制通过它的电流，而是它自身的电阻。
因此，如果您的PSU通过DMM驱动过高的电流，则如果电流在最高范围内变得过高，则切换到下一个更高的电流范围，或者保险丝熔断。
这种上升将降低DMM的内阻，因此可能进一步增加电流。
您可以使用手动量程，因此您具有恒定（更高）的阻力。
您可以在34461A的规格中间接找到每个电流范围内这些分流电阻的值。
我想，它对于100μA和1mA有100欧姆，对于10mA和100​​mA有2欧姆，对于1A和3A有0.1欧姆。
单独的10A范围可以具有6.4毫欧。
所有值都必须通过其他内部电阻来增加，请参阅负载电压规范。
这可能会限制您的电流（按欧姆定律）。
如果该固定范围又过载，则电路保护将被激活，即开关二极管电桥，它将使过载电流短路，从而进一步增加电流。
坦率



     以下为原文

  Your question is a bit strange, frankly speaking. I'll try to answer, hoping not having misinterpreted your question.

I fear you have the wrong concept in mind about how the current input works.

The current range of any DMM has an internal shunt (resistor) only.

It is neither a current sink / source, nor does such a shunt have the ability to limit the current through it in a controlled manner, but by its own resistance.

So if your PSU drives too high a current through the DMM, either this switches to the next higher current ranges, or the fuse blows, if the current gets too high in the highest range.

This up-ranging will decrease the inner resistance of the DMM, therefore maybe increasing the current further.

You may use manual ranging, so you have a constant (higher) resistance. You'll find the values of these shunt resistors per current range indirectly in the specification of the 34461A.
I guess, that it has 100 Ohm for 100µA and 1mA, 2 Ohm for 10mA and 100mA, 0.1 Ohm for 1 A and 3A.
The separate 10A range may have 6.4 milli-Ohm.
All values have to be increased by other internal resistances, see burden voltage specification.

This MAY limit your current (by Ohms law). If this fixed range is in turn overloaded, the circuit protection will be activated, that is a switched diode bridge, which will short cut the overload current, and therefore further increase the current.


Frank

弗兰克是对的。
数字万用表仅测量电流，它不会限制它，除非它在电流超过数字万用表的规格时熔断保险丝。
隐形。



     以下为原文

  Frank is right. The DMM only measures current, it does not limit it unless it blows the fuse when the current exceeds the specs of the DMM.
Stealth.

我认为需要做一些澄清，以避免用户混淆。
即使手动选择量程，如果电流超过所选范围，仪器也会改变分流器，以保护自身。
在这种情况下，屏幕上会显示“过载”通知，但电流会增加，直到输入保护保险丝的电源极限或额定值。
例如，测试由12V电池供电并选择最低范围的电路，这并不意味着电流将限制在120mA。
在短路中，它将“尝试”超过100A！
我认为这是大多数（如果不是全部）自动量程仪器处理这种情况的方式。
问候，Damianos



     以下为原文

  I think that some clarification is needed, to avoid confusion of users.
 
Even with a manual selection of range, the instrument will change the shunt if the current exceeds the selected range, to protect itself. In this case on the screen it will show  an "overload" notification, but the current will increase, up to the limit of the source or the rating of the input protection fuse.
 
For example testing a circuit that is powered from a 12V battery and selecting the lowest range, this does not mean that the current will be limited to 120mA. In a short circuit it will "try" to be more than 100A!
 
I think that this is the way that most (if not all) auto-range instruments are handling this situation.
 
Regards,
Damianos